1. Field of the Invention
The present invention pertains to wafer-type valves such as butterfly valves. Such valves typically include a relatively thin generally cylindrical valve body which is connected into a pipe line by being clamped between two flange fittings. The valve body has a flowway therethrough and a valve element, usually generally disc-shaped, is mounted in the flowway for movement from a closed valve position in which it lies transversely across the flowway to an open valve position in which it opens the flowway. The valve movement is usually rotation about an axis extending generally transversely across the flowway. Thus in the open valve position, the valve element lies generally parallel to the flowway centerline and extends beyond the axial extremities or end faces of the valve body.
2. Description of the Prior Art
In the past, some wafer valves of the type described above have had holes formed in their valve bodies for receipt of stud members such as bolts which also extend between the flange fittings to clamp the latter together. The placement of the studs through the holes in the valve body would serve to center the valve in place until the flange fittings could be firmly secured. Where the valve element is of the rotary type, such centering is necessary because the flowway through the valve body must be perfectly aligned with the flow passageways of the flange fittings and adjacent pipes in order to prevent interference between the valve element and the flanges during movement of the valve element between the closed and open positions. However, centering may also be desired in valve assemblies having valve elements other than rotary discs.
Problems arise in that the various flange fittings with which a particular type of valve will be used are not uniform. In particular, the size, number, and spacing of the stud members vary. In the past, it has been necessary to manufacture valves of one basic type in a number of forms each designed to be used with a particular type of flange fitting. The manufacture of various forms of a single basic type of valve body is not only unduly expensive, but still fails, in at least some cases, to ensure that all the types of flange fittings which may be encountered in the field can be properly accommodated.
In other prior wafer valves no holes are provided in the valve body. Instead, the valve body is centered between the flange fittings either manually or by means of a suitable tool. Centering the valve is this manner is extremely difficult and often results in an assembly in which the valve flowway is imperfectly aligned with the flow passageways in the flange fittings Consequently, a rotary disc valve member may jam against the flange fittings when it is rotated from closed to open positions, or other problems may result.